neon test globe help

[jinxsta]

Hi all while waiting for my star analyser to arrive I thought I would have a go a making a neon globe tester for calibration. Remebered reading about a 70 volt neon globe and a 270k resistor used to bring compatable with 240v somewhere but cant recall where is there anybody that has a diagram or page that has the details. Have he neon globes and a 270k 1watt resistor and a switch rated for 250v.Any help or a point in the right direction would be helpfully.

Thanks in advance
Daniel.

[Merlin66]

Daniel,
I got mine already set-up for 220V from Jaycar. It's just a Neon indicator lamp, and remove the bulb from the green/ red housing.
Looking at it, the resistor just seems to be soldered to one of the bulb legs in parallel; (this, based on whatever the resistance of the bulb is, assuming 100K, would drop the voltage to around the required 80V)
Hope this helps.

[jinxsta]

Thanks Merlin will look into jaycar online as the store here is next to useless, just a question do you have a switch connected or just plug to wall.

Thanks
Daniel

[Merlin66]

daniel,
I do both!
The Neon fitted to the Littrow has a switch to allow me to "flash" a reference spectrum; the other is fitted into a Foucault tester set-up and is just direct connect.
You can see it in the Littrow write-up
http://www.iceinspace.com.au/index.php?id=63,500,0,0,1,0

[kinetic]

I know it's stating the obvious but just be careful mucking about with
240v.
In the darkness, on a wet lawn/ dome using a scope etc....not
a good environment for 240v.
It's a pity about neons, they need about 40-80v to work.

I got mine (for the spectroscope calibration) from a 2nd-hand
powerpoint that had neons on the front.

See here (http://mywebsite.bigpond.com/astrosteve/cd_spectroscope.htm) for some pics of it through a webcam:

Steve

[Merlin66]

Steve,
I agree 100%!!!
I'm currently getting a low voltage invertor built to allow the Neon to be driven from a 9V input. This is a small PCB ( 50mm x 50mm) and would be mounted on the side of the Littrow and allow me to use either the 12V batteries or even a bundle of AA batteries... Keep you posted!!

[jinxsta]

Thanks Steve and merlin you guys have been both helpfull, point taken about 240v in the outdoors and will be putting all components in a sealed project box and on an rcd protected outlet.
thanks for the website Steve is very interesting.
also interested in the pcb run of a 9v or 12v source will look forward to the post.
I still have a lot to learn on talking spectrum and how to read them but should be a lot of fun.

Thanks again
Daniel

[Merlin66]

Guys,
The PCB circuit is based on one given in SILICON CHIP. ( From a circuit in Linear Technology site -www.linear-tech.com)
Called " Neon flasher runs from 3V supply"
Uses a IC LT1173.

[kinetic]

Some high intensity LED torches and garden solar lights have a
chopper circuit that supplies the LEDs with a high frequency DC
much higher than the LED would normally operate on.
Maybe a similar circuit could be modified a bit to excite a neon.
On my bench power supply none of the various neons I had would
glow until about 40v or higher.
Interesting stuff. Thanks for the SC link Merlin.

Steve

[jinxsta]

By a stroke of luck I had bought a 12 volt fluro work light the one you hold in your hand and plug into the cigarette lighter socket.
I pulled the hand end rubber cap off and it has a circuit board with a transformer and dohicky's (yes I know technical stuff).
Hooked up a neon globe from dicksmiths and it works nice and bright with 2 legs attached and dim with one leg atached (why that is I have no idea) so $7 for the light at bunnings and $0.44 at dicksmith looks like it might be a winner if I just find where I left my multi meter I would like to measure the output and do further testing as the light gets to hot to touch after a short time.but will keep going and maybe we can use it some how for a artificial neon star.

[jinxsta]

Well after some trial and error I managed to get it going with the board from the 12 volt fluoro car work light and a neon rocker switch that I carefully pulled apart and removed the neon globe and resistor.
I unsoldered the fluoro connections and soldered the neon globe with restistor.
Have attached a couple of photos.
Thanks to all for thier ideas.:thumbsup:
Jinxsta

[Merlin66]

Certainly looks interesting!!
What's the model # of the 12V torch you "modded"????
BTW to use a neon reference with the SA you'll need to fit a slit, see the notes I uploaded..

[jinxsta]

Don't have a model number but attached a pic of the light I got from bunnings.
I tried a few neon globes and different resistors but kept burning them out, so I used the globe from a neon rocker switch it allready had the resistor attached as you suggested and that seems to have done the trick, switch model number p7705 from dicksmiths. Just wish I could find my multi meter to see what the voltage is.
Maybe someone a little more electronically mined can figure out what it is.
Hope it helps
Jinxsta

[jinxsta]

Also going to have a play with a fibre optic toslink audio cable to see what happens maybe like an artificial star ? see what happens when I get to play with the SA if it ever arrives.
I'm only playing with a dvd spectroscope I made and so far looks ok.
And thanks for the read I'm sure there will be many more questions I need to ask looking, forward to get stuck into it all.
Jinxsta

[theodog]

Looks very interesting.:thumbsup:
For an artificial star try setting the light near a ball bearing as far as practical. Focus the scope on the image of the light on the BB (in a dark room).
I may be interested if you have any spare setups. When it comes to electronics I'm all thumbs, and blisters.:D

[Merlin66]

If you really want to consider fibre optics on spectroscopes, there's a few pitfalls along the way....
Richard's ongoing saga makes an interesting read!
http://tech.groups.yahoo.com/group/amateur_spectroscopy/?yguid=322612425
BTW did you import the SA direct from P-H in the UK?
remember I'm coming back to Oz in 3 weeks time....

[jinxsta]

Yes Merlin I ordered direct from P-H in the UK and thanks for the offer and the read is nice of you. The toslink cable idea is just that an idea I get a lot of ideas and sometimes I get lucky and one will work.

Theodog know what ya mean about blisters and thumbs wait till ya touch the end of the of the bare wires on this, and its still pluged in and switched on man it lit me up :eyepop: scared the hell outa me.
Jinxsta

[Robert9]

Depending on the type, neon globes will strike anywhere between 60 -100V. The little neon globes are probably of the type NE-2. The tube strikes when the voltage reaches about 65VAC and is extinguished when the voltage drops below 52VAC. For a 240VAC source, just use a 330Kohm resistor in series which will limit the current to about 0.5mA which is sufficient to keep it glowing. Or use a 270Kohm resistor for slightly more current 0.6mA (glows brighter).
Robert

[Merlin66]

So, what's the consensus opinion???
Is this the way to go to provide a safe low voltage supply to a reference Neon in the spectroscope???
(I've asked the kids to nick down to Bunnings and buy me one! Hopefully pick it up next month)

[jinxsta]

So far its a yes, globe will run for 2-3 mins no problem but the board gets hot even with the heat sink on it so I havent gone past the time limit.
Theodog will be trialing one when he gets it so fingers crossed.
I have put together 4 of them and have only smoked 1 board to point of it is buggered but it maybe a bad solder connection on my part or a dud board maybe. so grab a couple there only cheap.
Regards
Jinx

[jinxsta]

Oh forgot thanks for the explaination Robert is helpful.
on another note made another one with a toslink cable joiner glued to the box and still playing with it have attached some pics.Could be useful in getting the neon light onto a slit.

[Merlin66]

Daniel,
What size fibre optic are you using? I've tried 50 and 9 micron stuff.
BTW these can be used as an artificial star for testing the scope and spectroscope.
I found placing a small 6x6x6 prism just ahead of the slit and covering about 30% of the length gave a good comparison spectrum. I'd like to mount the PCB on the side of the spectroscope ( for convenience and safety).

[theodog]

Hi All,
I recieved Daniel's Neon Test Globe system today. I had planed to check it out this weekend but it got the better of me.
The unit looked very good, neat and well put together. The cord for the cig lighter was long enough to allow much distance between the car and telescope.
When pluged in and switched on the globe lit up with a soft orange glow.
The following spectrum of the globe was taken after finding the right region of spectrum through my HM spectroscope, with a 200mm camera lens.
In all I had the globe on for ~30-40 minutes. The 'black box' got warm but not enough to make me uncomfortable with it in the cool air of my shed.
One suggestion I would give is to allow a standard 12v input socket for the power cable to allow it to be run through a power supply, is this possible?
Overall, great unit and will incorperate it into my next project.
Well done Daniel.:thumbsup::thumbsup:

[Merlin66]

I use the Buil graph in preference to the Vspec reference for Neon; it seems to have a better selection of ( realistic?) intensity peaks.
The oddball line you show doesn't appear! on Buil
http://www.astrosurf.com/buil/us/spe2/calib2/neon1.gif

This neon driver is sounding better and better by the day!!
Well done Daniel!!!
Any other feedback??

[jinxsta]

Thanks guys.
Merlin the fiber optic cable is just a cheap toslink cable 'plastic' not sure of the micron size? but a more expensive fiber optic toslink cable may have some sort of spec sheet on it I will look into it. The board is small and would fit into your spectroscope no probs.

Theodog The cable plug on the unit could be changed to what ever you needed but I'm not sure what a standard 12 volt plug looks like?
The spectrum pic looks good thanks for posting it up, I only have the SA and its been raining here or cloudy for weeks:sadeyes: have only seen it on a home made dvd stectroscope in a tube.

I have started the material gathering to build a proper spectroscope and the little ideas and bits of info are great but can see it will take me a while to get there but looking forward to it, have to get the hang of the SA first.
Thanks guys :D
Jinxsta.

[theodog]

Sorry Daniel, not ment to be critical at all, just a sugestion. I think its teriffic and it will get much use as is.
By 12v socket, one of those 6mm centre positive thingies often used with 12v transformers that plug into 240v.
Have fun with the SA100, you can get a surprising amount of detail with one.

[jinxsta]

Theodog yes you could but the 6mm plug on the end easy the tip is posative and he outa is negative.
I use RCA plugs for connections as well, tip positive, saves fumbling around in the dark easy to solder as is the plug end.

[MrB]

Be carefull of shorting when using RCA plugs as power connectors, both pos and neg are exposed.
If possible use the RCA socket on the supply side, problem is there are no panel mount RCA plugs for the draw side.
Or use something designed for the job, a power connector.

[jinxsta]

Sorry MrB I should have been more specific, yes you are right you could short out the conection thats why I put in a switch for on off. I mounted these on a plastic tool box with recharge gel cell bateries for a power box can run scope fan, or camera or dew heaters etc.
Thanks for heads ups.